fix(mysql/maridb): set isolation level for transaction not entire ses…

…sion (#11476)

lib/dialects/abstract/index.js

@@ -30,6 +30,7 @@ AbstractDialect.prototype.supports = {
   bulkDefault: false,
   schemas: false,
   transactions: true,
+  settingIsolationLevelDuringTransaction: true,
   transactionOptions: {
     type: false
   },

lib/dialects/abstract/query-generator/transaction.js

@@ -16,7 +16,7 @@ const TransactionQueries = {
       return;
     }
 
-    return `SET SESSION TRANSACTION ISOLATION LEVEL ${value};`;
+    return `SET TRANSACTION ISOLATION LEVEL ${value};`;
   },
 
   generateTransactionId() {

lib/dialects/mariadb/index.js

@@ -25,6 +25,7 @@ MariadbDialect.prototype.supports = _.merge(
     'LIMIT ON UPDATE': true,
     lock: true,
     forShare: 'LOCK IN SHARE MODE',
+    settingIsolationLevelDuringTransaction: false,
     schemas: true,
     inserts: {
       ignoreDuplicates: ' IGNORE',

lib/dialects/mysql/index.js

@@ -24,6 +24,7 @@ MysqlDialect.prototype.supports = _.merge(_.cloneDeep(AbstractDialect.prototype.
   'LIMIT ON UPDATE': true,
   lock: true,
   forShare: 'LOCK IN SHARE MODE',
+  settingIsolationLevelDuringTransaction: false,
   inserts: {
     ignoreDuplicates: ' IGNORE',
     updateOnDuplicate: ' ON DUPLICATE KEY UPDATE'

lib/transaction.js

@@ -129,7 +129,6 @@ class Transaction {
       .then(() => {
         return this.begin()
           .then(() => this.setDeferrable())
-          .then(() => this.setIsolationLevel())
           .catch(setupErr => this.rollback().finally(() => {
             throw setupErr;
           }));
@@ -142,13 +141,6 @@ class Transaction {
       });
   }
 
-  begin() {
-    return this
-      .sequelize
-      .getQueryInterface()
-      .startTransaction(this, this.options);
-  }
-
   setDeferrable() {
     if (this.options.deferrable) {
       return this
@@ -158,11 +150,18 @@ class Transaction {
     }
   }
 
-  setIsolationLevel() {
-    return this
-      .sequelize
-      .getQueryInterface()
-      .setIsolationLevel(this, this.options.isolationLevel, this.options);
+  begin() {
+    const queryInterface = this.sequelize.getQueryInterface();
+
+    if ( this.sequelize.dialect.supports.settingIsolationLevelDuringTransaction ) {
+      return queryInterface.startTransaction(this, this.options).then(() => {
+        return queryInterface.setIsolationLevel(this, this.options.isolationLevel, this.options);
+      });
+    }
+
+    return queryInterface.setIsolationLevel(this, this.options.isolationLevel, this.options).then(() => {
+      return queryInterface.startTransaction(this, this.options);
+    });
   }
 
   cleanup() {

test/integration/transaction.test.js

@@ -527,6 +527,77 @@ if (current.dialect.supports.transactions) {
 
     }
 
+    describe('isolation levels', () => {
+      it('should read the most recent committed rows when using the READ COMMITTED isolation level', function() {
+        const User = this.sequelize.define('user', {
+          username: Support.Sequelize.STRING
+        });
+
+        return expect(
+          this.sequelize.sync({ force: true }).then(() => {
+            return this.sequelize.transaction({ isolationLevel: Transaction.ISOLATION_LEVELS.READ_COMMITTED }, transaction => {
+              return User.findAll({ transaction })
+                .then(users => expect( users ).to.have.lengthOf(0))
+                .then(() => User.create({ username: 'jan' })) // Create a User outside of the transaction
+                .then(() => User.findAll({ transaction }))
+                .then(users => expect( users ).to.have.lengthOf(1)); // We SHOULD see the created user inside the transaction
+            });
+          })
+        ).to.eventually.be.fulfilled;
+      });
+
+      // mssql is excluded because it implements REPREATABLE READ using locks rather than a snapshot, and will see the new row
+      if (!['sqlite', 'mssql'].includes(dialect)) {
+        it('should not read newly committed rows when using the REPEATABLE READ isolation level', function() {
+          const User = this.sequelize.define('user', {
+            username: Support.Sequelize.STRING
+          });
+
+          return expect(
+            this.sequelize.sync({ force: true }).then(() => {
+              return this.sequelize.transaction({ isolationLevel: Transaction.ISOLATION_LEVELS.REPEATABLE_READ }, transaction => {
+                return User.findAll({ transaction })
+                  .then(users => expect( users ).to.have.lengthOf(0))
+                  .then(() => User.create({ username: 'jan' })) // Create a User outside of the transaction
+                  .then(() => User.findAll({ transaction })) 
+                  .then(users => expect( users ).to.have.lengthOf(0)); // We SHOULD NOT see the created user inside the transaction
+              });
+            })
+          ).to.eventually.be.fulfilled;
+        });
+      }
+
+      // PostgreSQL is excluded because it detects Serialization Failure on commit instead of acquiring locks on the read rows
+      if (!['sqlite', 'postgres', 'postgres-native'].includes(dialect)) {
+        it('should block updates after reading a row using SERIALIZABLE', function() {
+          const User = this.sequelize.define('user', {
+              username: Support.Sequelize.STRING
+            }),
+            transactionSpy = sinon.spy();
+
+          return this.sequelize.sync({ force: true }).then(() => {
+            return User.create({ username: 'jan' });
+          }).then(() => {
+            return this.sequelize.transaction({ isolationLevel: Transaction.ISOLATION_LEVELS.SERIALIZABLE }).then(transaction => {
+              return User.findAll( { transaction } )
+                .then(() => Promise.join(
+                  User.update({ username: 'joe' }, {
+                    where: {
+                      username: 'jan'
+                    }
+                  }).then(() => expect(transactionSpy).to.have.been.called ), // Update should not succeed before transaction has committed
+                  Promise.delay(2000)
+                    .then(() => transaction.commit())
+                    .then(transactionSpy)
+                ));
+            });
+          });
+        });
+      }
+
+    });
+
+
     if (current.dialect.supports.lock) {
       describe('row locking', () => {
         it('supports for update', function() {

test/unit/transaction.test.js

@@ -50,4 +50,28 @@ describe('Transaction', () => {
       return Sequelize.Promise.resolve();
     });
   });
+
+  it('should set isolation level correctly', function() {
+    const expectations = {
+      all: [
+        'SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;',
+        'START TRANSACTION;'
+      ],
+      postgres: [
+        'START TRANSACTION;',
+        'SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;'
+      ],
+      sqlite: [
+        'BEGIN DEFERRED TRANSACTION;',
+        'PRAGMA read_uncommitted = ON;'
+      ],
+      mssql: [
+        'BEGIN TRANSACTION;'
+      ]
+    };
+    return current.transaction({ isolationLevel: Sequelize.Transaction.ISOLATION_LEVELS.READ_UNCOMMITTED }, () => {
+      expect(this.stub.args.map(arg => arg[0])).to.deep.equal(expectations[dialect] || expectations.all);
+      return Sequelize.Promise.resolve();
+    });
+  });
 });